This will allow to use generic refcount_t interfaces to check counters
overflow instead of currently existing VM_BUG_ON().  The only difference
after the patch is VM_BUG_ON() may cause BUG(), while refcount_t fires
with WARN().  But this seems not to be significant here, since such the
problems are usually caught by syzbot with panic-on-warn enabled.

Link: http://lkml.kernel.org/r/153910718919.7006.13400779039257185427.stgit@localhost.localdomain
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

If move_freepages_block() returns 0 because !zone_spans_pfn(),
*num_movable can hold the value from the stack because it does not get
initialized in move_freepages().

Move the initialization to move_freepages_block() to guarantee the value
actually makes sense.

This currently doesn't affect its only caller where num_movable != NULL,
so no bug fix, but just more robust.

Link: http://lkml.kernel.org/r/alpine.DEB.2.21.1810051355490.212229@chino.kir.corp.google.com
Signed-off-by: David Rientjes <rientjes@google.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Greg Thelen <gthelen@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Replace "fallthru" with a proper "fall through" annotation.

This fix is part of the ongoing efforts to enabling
-Wimplicit-fallthrough

Link: http://lkml.kernel.org/r/20181003105114.GA24423@embeddedor.com
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Now we recycle the uffd servicing threads earlier than the lock threads.
It might happen that when the lock thread is still blocked at a pthread
mutex lock while the servicing thread has already quitted for the cpu so
the lock thread will be blocked forever and hang the test program.  To fix
the possible race, recycle the lock threads first.

This never happens with current missing-only tests, but when I start to
run the write-protection tests (the feature is not yet posted upstream) it
happens every time of the run possibly because in that new test we'll need
to service two page faults for each lock operation.

Link: http://lkml.kernel.org/r/20180930074259.18229-4-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Acked-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Zi Yan <zi.yan@cs.rutgers.edu>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Shaohua Li <shli@fb.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

We do very similar things in read and poll modes, but we're copying the
codes around.  Share the codes properly on reading the message and
handling the page fault to make the code cleaner.  Meanwhile this solves
previous mismatch of behaviors between the two modes on that the old code:

- did not check EAGAIN case in read() mode
- ignored BOUNCE_VERIFY check in read() mode

Link: http://lkml.kernel.org/r/20180930074259.18229-3-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Acked-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Zi Yan <zi.yan@cs.rutgers.edu>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Shaohua Li <shli@fb.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Firstly, the help in the comment region is obsolete, now we support
three parameters.  Since at it, change it and move it into the help
message of the program.

Also, the help messages dumped here and there is obsolete too.  Use a
single usage() helper.

Link: http://lkml.kernel.org/r/20180930074259.18229-2-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Acked-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Zi Yan <zi.yan@cs.rutgers.edu>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Shaohua Li <shli@fb.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Having two gigantic arrays that must manually be kept in sync, including
ifdefs, isn't exactly robust.  To make it easier to catch such issues in
the future, add a BUILD_BUG_ON().

Link: http://lkml.kernel.org/r/20181001143138.95119-3-jannh@google.com
Signed-off-by: Jann Horn <jannh@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: Kemi Wang <kemi.wang@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

We clear the pte temporarily during read/modify/write update of the pte.
If we take a page fault while the pte is cleared, the application can get
SIGBUS.  One such case is with remap_pfn_range without a backing
vm_ops->fault callback.  do_fault will return SIGBUS in that case.

cpu 0		 				cpu1
mprotect()
ptep_modify_prot_start()/pte cleared.
.
.						page fault.
.
.
prep_modify_prot_commit()

Fix this by taking page table lock and rechecking for pte_none.

[aneesh.kumar@linux.ibm.com: fix crash observed with syzkaller run]
  Link: http://lkml.kernel.org/r/87va6bwlfg.fsf@linux.ibm.com
Link: http://lkml.kernel.org/r/20180926031858.9692-1-aneesh.kumar@linux.ibm.com
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Ido Schimmel <idosch@idosch.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The comment for PFN_SPECIAL is missed in pfn_t.h. Add comment to get
consistent with other pfn flags.

Link: http://lkml.kernel.org/r/1538086549-100536-1-git-send-email-yang.shi@linux.alibaba.com
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Suggested-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

brk might be used to shrink memory mapping too other than munmap().  So,
it may hold write mmap_sem for long time when shrinking large mapping, as
what commit ("mm: mmap: zap pages with read mmap_sem in munmap")
described.

The brk() will not manipulate vmas anymore after __do_munmap() call for
the mapping shrink use case.  But, it may set mm->brk after __do_munmap(),
which needs hold write mmap_sem.

However, a simple trick can workaround this by setting mm->brk before
__do_munmap().  Then restore the original value if __do_munmap() fails.
With this trick, it is safe to downgrade to read mmap_sem.

So, the same optimization, which downgrades mmap_sem to read for zapping
pages, is also feasible and reasonable to this case.

The period of holding exclusive mmap_sem for shrinking large mapping would
be reduced significantly with this optimization.

[akpm@linux-foundation.org: tweak comment]
[yang.shi@linux.alibaba.com: fix unsigned compare against 0 issue]
  Link: http://lkml.kernel.org/r/1538687672-17795-1-git-send-email-yang.shi@linux.alibaba.com
Link: http://lkml.kernel.org/r/1538067582-60038-2-git-send-email-yang.shi@linux.alibaba.com
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Cc: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Other than munmap, mremap might be used to shrink memory mapping too.
So, it may hold write mmap_sem for long time when shrinking large
mapping, as what commit ("mm: mmap: zap pages with read mmap_sem in
munmap") described.

The mremap() will not manipulate vmas anymore after __do_munmap() call for
the mapping shrink use case, so it is safe to downgrade to read mmap_sem.

So, the same optimization, which downgrades mmap_sem to read for zapping
pages, is also feasible and reasonable to this case.

The period of holding exclusive mmap_sem for shrinking large mapping
would be reduced significantly with this optimization.

MREMAP_FIXED and MREMAP_MAYMOVE are more complicated to adopt this
optimization since they need manipulate vmas after do_munmap(),
downgrading mmap_sem may create race window.

Simple mapping shrink is the low hanging fruit, and it may cover the
most cases of unmap with munmap together.

[akpm@linux-foundation.org: tweak comment]
[yang.shi@linux.alibaba.com: fix unsigned compare against 0 issue]
  Link: http://lkml.kernel.org/r/1538687672-17795-2-git-send-email-yang.shi@linux.alibaba.com
Link: http://lkml.kernel.org/r/1538067582-60038-1-git-send-email-yang.shi@linux.alibaba.com
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Cc: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

These codes can be replaced with new inline vmf_error().

Link: http://lkml.kernel.org/r/20180927171411.GA23331@jordon-HP-15-Notebook-PC
Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ia64, mips, parisc, powerpc, sh, sparc, x86 architectures use the same
version of huge_ptep_get, so move this generic implementation into
asm-generic/hugetlb.h.

[arnd@arndb.de: fix ARM 3level page tables]
  Link: http://lkml.kernel.org/r/20181005161722.904274-1-arnd@arndb.de
Link: http://lkml.kernel.org/r/20180920060358.16606-12-alex@ghiti.fr
Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Tested-by: Helge Deller <deller@gmx.de>			[parisc]
Acked-by: Catalin Marinas <catalin.marinas@arm.com>	[arm64]
Acked-by: Paul Burton <paul.burton@mips.com>		[MIPS]
Acked-by: Ingo Molnar <mingo@kernel.org>		[x86]
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James E.J. Bottomley <jejb@parisc-linux.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arm, ia64, sh, x86 architectures use the same version
of huge_ptep_set_access_flags, so move this generic implementation
into asm-generic/hugetlb.h.

Link: http://lkml.kernel.org/r/20180920060358.16606-11-alex@ghiti.fr
Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Tested-by: Helge Deller <deller@gmx.de>			[parisc]
Acked-by: Catalin Marinas <catalin.marinas@arm.com>	[arm64]
Acked-by: Paul Burton <paul.burton@mips.com>		[MIPS]
Acked-by: Ingo Molnar <mingo@kernel.org>		[x86]
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James E.J. Bottomley <jejb@parisc-linux.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arm, ia64, mips, powerpc, sh, x86 architectures use the same version of
huge_ptep_set_wrprotect, so move this generic implementation into
asm-generic/hugetlb.h.

Link: http://lkml.kernel.org/r/20180920060358.16606-10-alex@ghiti.fr
Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Tested-by: Helge Deller <deller@gmx.de>			[parisc]
Acked-by: Catalin Marinas <catalin.marinas@arm.com>	[arm64]
Acked-by: Paul Burton <paul.burton@mips.com>		[MIPS]
Acked-by: Ingo Molnar <mingo@kernel.org>		[x86]
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James E.J. Bottomley <jejb@parisc-linux.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arm, arm64, powerpc, sparc, x86 architectures use the same version of
prepare_hugepage_range, so move this generic implementation into
asm-generic/hugetlb.h.

Link: http://lkml.kernel.org/r/20180920060358.16606-9-alex@ghiti.fr
Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Tested-by: Helge Deller <deller@gmx.de>			[parisc]
Acked-by: Catalin Marinas <catalin.marinas@arm.com>	[arm64]
Acked-by: Paul Burton <paul.burton@mips.com>		[MIPS]
Acked-by: Ingo Molnar <mingo@kernel.org>		[x86]
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James E.J. Bottomley <jejb@parisc-linux.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arm, arm64, ia64, mips, parisc, powerpc, sh, sparc, x86 architectures use
the same version of huge_pte_wrprotect, so move this generic
implementation into asm-generic/hugetlb.h.

Link: http://lkml.kernel.org/r/20180920060358.16606-8-alex@ghiti.fr
Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Tested-by: Helge Deller <deller@gmx.de>			[parisc]
Acked-by: Catalin Marinas <catalin.marinas@arm.com>	[arm64]
Acked-by: Paul Burton <paul.burton@mips.com>		[MIPS]
Acked-by: Ingo Molnar <mingo@kernel.org>		[x86]
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James E.J. Bottomley <jejb@parisc-linux.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arm, arm64, ia64, mips, parisc, powerpc, sh, sparc, x86 architectures use
the same version of huge_pte_none, so move this generic implementation
into asm-generic/hugetlb.h.

Link: http://lkml.kernel.org/r/20180920060358.16606-7-alex@ghiti.fr
Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Tested-by: Helge Deller <deller@gmx.de>			[parisc]
Acked-by: Catalin Marinas <catalin.marinas@arm.com>	[arm64]
Acked-by: Paul Burton <paul.burton@mips.com>		[MIPS]
Acked-by: Ingo Molnar <mingo@kernel.org>		[x86]
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James E.J. Bottomley <jejb@parisc-linux.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arm, x86 architectures use the same version of huge_ptep_clear_flush, so
move this generic implementation into asm-generic/hugetlb.h.

Link: http://lkml.kernel.org/r/20180920060358.16606-6-alex@ghiti.fr
Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Tested-by: Helge Deller <deller@gmx.de>			[parisc]
Acked-by: Catalin Marinas <catalin.marinas@arm.com>	[arm64]
Acked-by: Paul Burton <paul.burton@mips.com>		[MIPS]
Acked-by: Ingo Molnar <mingo@kernel.org>		[x86]
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James E.J. Bottomley <jejb@parisc-linux.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arm, ia64, sh, x86 architectures use the same version of
huge_ptep_get_and_clear, so move this generic implementation into
asm-generic/hugetlb.h.

Link: http://lkml.kernel.org/r/20180920060358.16606-5-alex@ghiti.fr
Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Tested-by: Helge Deller <deller@gmx.de>			[parisc]
Acked-by: Catalin Marinas <catalin.marinas@arm.com>	[arm64]
Acked-by: Paul Burton <paul.burton@mips.com>		[MIPS]
Acked-by: Ingo Molnar <mingo@kernel.org>		[x86]
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James E.J. Bottomley <jejb@parisc-linux.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arm, ia64, mips, powerpc, sh, x86 architectures use the same version of
set_huge_pte_at, so move this generic implementation into
asm-generic/hugetlb.h.

Link: http://lkml.kernel.org/r/20180920060358.16606-4-alex@ghiti.fr
Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Tested-by: Helge Deller <deller@gmx.de>			[parisc]
Acked-by: Catalin Marinas <catalin.marinas@arm.com>	[arm64]
Acked-by: Paul Burton <paul.burton@mips.com>		[MIPS]
Acked-by: Ingo Molnar <mingo@kernel.org>		[x86]
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James E.J. Bottomley <jejb@parisc-linux.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arm, arm64, mips, parisc, sh, x86 architectures use the same version of
hugetlb_free_pgd_range, so move this generic implementation into
asm-generic/hugetlb.h.

Link: http://lkml.kernel.org/r/20180920060358.16606-3-alex@ghiti.fr
Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Tested-by: Helge Deller <deller@gmx.de>			[parisc]
Acked-by: Catalin Marinas <catalin.marinas@arm.com>	[arm64]
Acked-by: Paul Burton <paul.burton@mips.com>		[MIPS]
Acked-by: Ingo Molnar <mingo@kernel.org>		[x86]
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James E.J. Bottomley <jejb@parisc-linux.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

In order to reduce copy/paste of functions across architectures and then
make riscv hugetlb port (and future ports) simpler and smaller, this
patchset intends to factorize the numerous hugetlb primitives that are
defined across all the architectures.

Except for prepare_hugepage_range, this patchset moves the versions that
are just pass-through to standard pte primitives into
asm-generic/hugetlb.h by using the same #ifdef semantic that can be found
in asm-generic/pgtable.h, i.e.  __HAVE_ARCH_***.

s390 architecture has not been tackled in this serie since it does not use
asm-generic/hugetlb.h at all.

This patchset has been compiled on all addressed architectures with
success (except for parisc, but the problem does not come from this
series).

This patch (of 11):

asm-generic/hugetlb.h proposes generic implementations of hugetlb related
functions: use __HAVE_ARCH_HUGE* defines in order to make arch specific
implementations of hugetlb functions consistent with pgtable.h scheme.

Link: http://lkml.kernel.org/r/20180920060358.16606-2-alex@ghiti.fr
Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>	[arm64]
Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Burton <paul.burton@mips.com>
Cc: James Hogan <jhogan@kernel.org>
Cc: James E.J. Bottomley <jejb@parisc-linux.org>
Cc: Helge Deller <deller@gmx.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>		[x86]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The local variable `addr' in __get_user_pages_fast() is just a shadow of
`start'.  Since `start' never changes after assignment to `addr', it is
fine to replace `start' with it.

Also the meaning of [start, end] is more obvious than [addr, end] when
passed to gup_pgd_range().

Link: http://lkml.kernel.org/r/20180925021448.20265-1-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The ZONE_DEVICE pages were being initialized in two locations.  One was
with the memory_hotplug lock held and another was outside of that lock.
The problem with this is that it was nearly doubling the memory
initialization time.  Instead of doing this twice, once while holding a
global lock and once without, I am opting to defer the initialization to
the one outside of the lock.  This allows us to avoid serializing the
overhead for memory init and we can instead focus on per-node init times.

One issue I encountered is that devm_memremap_pages and
hmm_devmmem_pages_create were initializing only the pgmap field the same
way.  One wasn't initializing hmm_data, and the other was initializing it
to a poison value.  Since this is something that is exposed to the driver
in the case of hmm I am opting for a third option and just initializing
hmm_data to 0 since this is going to be exposed to unknown third party
drivers.

[alexander.h.duyck@linux.intel.com: fix reference count for pgmap in devm_memremap_pages]
  Link: http://lkml.kernel.org/r/20181008233404.1909.37302.stgit@localhost.localdomain
Link: http://lkml.kernel.org/r/20180925202053.3576.66039.stgit@localhost.localdomain
Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Reviewed-by: Pavel Tatashin <pavel.tatashin@microsoft.com>
Tested-by: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

It doesn't make much sense to use the atomic SetPageReserved at init time
when we are using memset to clear the memory and manipulating the page
flags via simple "&=" and "|=" operations in __init_single_page.

This patch adds a non-atomic version __SetPageReserved that can be used
during page init and shows about a 10% improvement in initialization times
on the systems I have available for testing.  On those systems I saw
initialization times drop from around 35 seconds to around 32 seconds to
initialize a 3TB block of persistent memory.  I believe the main advantage
of this is that it allows for more compiler optimization as the __set_bit
operation can be reordered whereas the atomic version cannot.

I tried adding a bit of documentation based on f1dd2cd1

 ("mm,
memory_hotplug: do not associate hotadded memory to zones until online").

Ideally the reserved flag should be set earlier since there is a brief
window where the page is initialization via __init_single_page and we have
not set the PG_Reserved flag.  I'm leaving that for a future patch set as
that will require a more significant refactor.

Link: http://lkml.kernel.org/r/20180925202018.3576.11607.stgit@localhost.localdomain
Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Reviewed-by: Pavel Tatashin <pavel.tatashin@microsoft.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Patch series "Address issues slowing persistent memory initialization", v5.

The main thing this patch set achieves is that it allows us to initialize
each node worth of persistent memory independently.  As a result we reduce
page init time by about 2 minutes because instead of taking 30 to 40
seconds per node and going through each node one at a time, we process all
4 nodes in parallel in the case of a 12TB persistent memory setup spread
evenly over 4 nodes.

This patch (of 3):

On systems with a large amount of memory it can take a significant amount
of time to initialize all of the page structs with the PAGE_POISON_PATTERN
value.  I have seen it take over 2 minutes to initialize a system with
over 12TB of RAM.

In order to work around the issue I had to disable CONFIG_DEBUG_VM and
then the boot time returned to something much more reasonable as the
arch_add_memory call completed in milliseconds versus seconds.  However in
doing that I had to disable all of the other VM debugging on the system.

In order to work around a kernel that might have CONFIG_DEBUG_VM enabled
on a system that has a large amount of memory I have added a new kernel
parameter named "vm_debug" that can be set to "-" in order to disable it.

Link: http://lkml.kernel.org/r/20180925201921.3576.84239.stgit@localhost.localdomain
Reviewed-by: Pavel Tatashin <pavel.tatashin@microsoft.com>
Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The flag memcg_kmem_skip_account was added during the era of opt-out kmem
accounting.  There is no need for such flag in the opt-in world as there
aren't any __GFP_ACCOUNT allocations within memcg_create_cache_enqueue().

Link: http://lkml.kernel.org/r/20180919004501.178023-1-shakeelb@google.com
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Greg Thelen <gthelen@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This patch, as the previous one, gets rid of the wrong if statements.
While at it, I realized that the comments are sometimes very confusing,
to say the least, and wrong.
For example:

___
zone_last = ZONE_MOVABLE;

/*
 * check whether node_states[N_HIGH_MEMORY] will be changed
 * If we try to offline the last present @nr_pages from the node,
 * we can determind we will need to clear the node from
 * node_states[N_HIGH_MEMORY].
 */

for (; zt <= zone_last; zt++)
        present_pages += pgdat->node_zones[zt].present_pages;
if (nr_pages >= present_pages)
        arg->status_change_nid = zone_to_nid(zone);
else
        arg->status_change_nid = -1;
___

In case the node gets empry, it must be removed from N_MEMORY.  We already
check N_HIGH_MEMORY a bit above within the CONFIG_HIGHMEM ifdef code.  Not
to say that status_change_nid is for N_MEMORY, and not for N_HIGH_MEMORY.

So I re-wrote some of the comments to what I think is better.

[osalvador@suse.de: address feedback from Pavel]
  Link: http://lkml.kernel.org/r/20180921132634.10103-5-osalvador@techadventures.net
Link: http://lkml.kernel.org/r/20180919100819.25518-6-osalvador@techadventures.net
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Pavel Tatashin <pavel.tatashin@microsoft.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: <yasu.isimatu@gmail.com>
Cc: Mathieu Malaterre <malat@debian.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

While looking at node_states_check_changes_online, I stumbled upon some
confusing things.

Right after entering the function, we find this:

if (N_MEMORY == N_NORMAL_MEMORY)
        zone_last = ZONE_MOVABLE;

This is wrong.
N_MEMORY cannot really be equal to N_NORMAL_MEMORY.
My guess is that this wanted to be something like:

if (N_NORMAL_MEMORY == N_HIGH_MEMORY)

to check if we have CONFIG_HIGHMEM.

Later on, in the CONFIG_HIGHMEM block, we have:

if (N_MEMORY == N_HIGH_MEMORY)
        zone_last = ZONE_MOVABLE;

Again, this is wrong, and will never be evaluated to true.

Besides removing these wrong if statements, I simplified the function a
bit.

[osalvador@suse.de: address feedback from Pavel]
  Link: http://lkml.kernel.org/r/20180921132634.10103-4-osalvador@techadventures.net
Link: http://lkml.kernel.org/r/20180919100819.25518-5-osalvador@techadventures.net
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Pavel Tatashin <pavel.tatashin@microsoft.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Mathieu Malaterre <malat@debian.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: <yasu.isimatu@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

node_states_clear has the following if statements:

if ((N_MEMORY != N_NORMAL_MEMORY) &&
    (arg->status_change_nid_high >= 0))
        ...

if ((N_MEMORY != N_HIGH_MEMORY) &&
    (arg->status_change_nid >= 0))
        ...

N_MEMORY can never be equal to neither N_NORMAL_MEMORY nor
N_HIGH_MEMORY.

Similar problem was found in [1].
Since this is wrong, let us get rid of it.

[1] https://patchwork.kernel.org/patch/10579155/

Link: http://lkml.kernel.org/r/20180919100819.25518-4-osalvador@techadventures.net
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Pavel Tatashin <pavel.tatashin@microsoft.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Mathieu Malaterre <malat@debian.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: <yasu.isimatu@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

In node_states_check_changes_online, we check if the node will have to be
set for any of the N_*_MEMORY states after the pages have been onlined.

Later on, we perform the activation in node_states_set_node.  Currently,
in node_states_set_node we set the node to N_MEMORY unconditionally.

This means that we call node_set_state for N_MEMORY every time pages go
online, but we only need to do it if the node has not yet been set for
N_MEMORY.

Fix this by checking status_change_nid.

Link: http://lkml.kernel.org/r/20180919100819.25518-2-osalvador@techadventures.net
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Pavel Tatashin <pavel.tatashin@microsoft.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: <yasu.isimatu@gmail.com>
Cc: Mathieu Malaterre <malat@debian.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Use the variable write_len instead of ov_iter_count(from).

Link: http://lkml.kernel.org/r/1537375855-2088-1-git-send-email-leviathan0992@gmail.com
Signed-off-by: haiqing.shq <leviathan0992@gmail.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

When unmapping VM_PFNMAP mappings, vm flags need to be updated.  Since the
vmas have been detached, so it sounds safe to update vm flags with read
mmap_sem.

Link: http://lkml.kernel.org/r/1537376621-51150-4-git-send-email-yang.shi@linux.alibaba.com
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Reviewed-by: Matthew Wilcox <willy@infradead.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

When unmapping VM_HUGETLB mappings, vm flags need to be updated.  Since
the vmas have been detached, so it sounds safe to update vm flags with
read mmap_sem.

Link: http://lkml.kernel.org/r/1537376621-51150-3-git-send-email-yang.shi@linux.alibaba.com
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Reviewed-by: Matthew Wilcox <willy@infradead.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Patch series "mm: zap pages with read mmap_sem in munmap for large
mapping", v11.

Background:
Recently, when we ran some vm scalability tests on machines with large memory,
we ran into a couple of mmap_sem scalability issues when unmapping large memory
space, please refer to https://lkml.org/lkml/2017/12/14/733 and
https://lkml.org/lkml/2018/2/20/576.

History:
Then akpm suggested to unmap large mapping section by section and drop mmap_sem
at a time to mitigate it (see https://lkml.org/lkml/2018/3/6/784).

V1 patch series was submitted to the mailing list per Andrew's suggestion
(see https://lkml.org/lkml/2018/3/20/786).  Then I received a lot great
feedback and suggestions.

Then this topic was discussed on LSFMM summit 2018.  In the summit, Michal
Hocko suggested (also in the v1 patches review) to try "two phases"
approach.  Zapping pages with read mmap_sem, then doing via cleanup with
write mmap_sem (for discussion detail, see
https://lwn.net/Articles/753269/)

Approach:
Zapping pages is the most time consuming part, according to the suggestion from
Michal Hocko [1], zapping pages can be done with holding read mmap_sem, like
what MADV_DONTNEED does. Then re-acquire write mmap_sem to cleanup vmas.

But, we can't call MADV_DONTNEED directly, since there are two major drawbacks:
  * The unexpected state from PF if it wins the race in the middle of munmap.
    It may return zero page, instead of the content or SIGSEGV.
  * Can't handle VM_LOCKED | VM_HUGETLB | VM_PFNMAP and uprobe mappings, which
    is a showstopper from akpm

But, some part may need write mmap_sem, for example, vma splitting. So,
the design is as follows:
        acquire write mmap_sem
        lookup vmas (find and split vmas)
        deal with special mappings
        detach vmas
        downgrade_write

        zap pages
        free page tables
        release mmap_sem

The vm events with read mmap_sem may come in during page zapping, but
since vmas have been detached before, they, i.e.  page fault, gup, etc,
will not be able to find valid vma, then just return SIGSEGV or -EFAULT as
expected.

If the vma has VM_HUGETLB | VM_PFNMAP, they are considered as special
mappings.  They will be handled by falling back to regular do_munmap()
with exclusive mmap_sem held in this patch since they may update vm flags.

But, with the "detach vmas first" approach, the vmas have been detached
when vm flags are updated, so it sounds safe to update vm flags with read
mmap_sem for this specific case.  So, VM_HUGETLB and VM_PFNMAP will be
handled by using the optimized path in the following separate patches for
bisectable sake.

Unmapping uprobe areas may need update mm flags (MMF_RECALC_UPROBES).
However it is fine to have false-positive MMF_RECALC_UPROBES according to
uprobes developer.  So, uprobe unmap will not be handled by the regular
path.

With the "detach vmas first" approach we don't have to re-acquire mmap_sem
again to clean up vmas to avoid race window which might get the address
space changed since downgrade_write() doesn't release the lock to lead
regression, which simply downgrades to read lock.

And, since the lock acquire/release cost is managed to the minimum and
almost as same as before, the optimization could be extended to any size
of mapping without incurring significant penalty to small mappings.

For the time being, just do this in munmap syscall path.  Other
vm_munmap() or do_munmap() call sites (i.e mmap, mremap, etc) remain
intact due to some implementation difficulties since they acquire write
mmap_sem from very beginning and hold it until the end, do_munmap() might
be called in the middle.  But, the optimized do_munmap would like to be
called without mmap_sem held so that we can do the optimization.  So, if
we want to do the similar optimization for mmap/mremap path, I'm afraid we
would have to redesign them.  mremap might be called on very large area
depending on the usecases, the optimization to it will be considered in
the future.

This patch (of 3):

When running some mmap/munmap scalability tests with large memory (i.e.
> 300GB), the below hung task issue may happen occasionally.

INFO: task ps:14018 blocked for more than 120 seconds.
       Tainted: G            E 4.9.79-009.ali3000.alios7.x86_64 #1
 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this
message.
 ps              D    0 14018      1 0x00000004
  ffff885582f84000 ffff885e8682f000 ffff880972943000 ffff885ebf499bc0
  ffff8828ee120000 ffffc900349bfca8 ffffffff817154d0 0000000000000040
  00ffffff812f872a ffff885ebf499bc0 024000d000948300 ffff880972943000
 Call Trace:
  [<ffffffff817154d0>] ? __schedule+0x250/0x730
  [<ffffffff817159e6>] schedule+0x36/0x80
  [<ffffffff81718560>] rwsem_down_read_failed+0xf0/0x150
  [<ffffffff81390a28>] call_rwsem_down_read_failed+0x18/0x30
  [<ffffffff81717db0>] down_read+0x20/0x40
  [<ffffffff812b9439>] proc_pid_cmdline_read+0xd9/0x4e0
  [<ffffffff81253c95>] ? do_filp_open+0xa5/0x100
  [<ffffffff81241d87>] __vfs_read+0x37/0x150
  [<ffffffff812f824b>] ? security_file_permission+0x9b/0xc0
  [<ffffffff81242266>] vfs_read+0x96/0x130
  [<ffffffff812437b5>] SyS_read+0x55/0xc0
  [<ffffffff8171a6da>] entry_SYSCALL_64_fastpath+0x1a/0xc5

It is because munmap holds mmap_sem exclusively from very beginning to all
the way down to the end, and doesn't release it in the middle.  When
unmapping large mapping, it may take long time (take ~18 seconds to unmap
320GB mapping with every single page mapped on an idle machine).

Zapping pages is the most time consuming part, according to the suggestion
from Michal Hocko [1], zapping pages can be done with holding read
mmap_sem, like what MADV_DONTNEED does.  Then re-acquire write mmap_sem to
cleanup vmas.

But, some part may need write mmap_sem, for example, vma splitting. So,
the design is as follows:
        acquire write mmap_sem
        lookup vmas (find and split vmas)
        deal with special mappings
        detach vmas
        downgrade_write

        zap pages
        free page tables
        release mmap_sem

The vm events with read mmap_sem may come in during page zapping, but
since vmas have been detached before, they, i.e.  page fault, gup, etc,
will not be able to find valid vma, then just return SIGSEGV or -EFAULT as
expected.

If the vma has VM_HUGETLB | VM_PFNMAP, they are considered as special
mappings.  They will be handled by without downgrading mmap_sem in this
patch since they may update vm flags.

But, with the "detach vmas first" approach, the vmas have been detached
when vm flags are updated, so it sounds safe to update vm flags with read
mmap_sem for this specific case.  So, VM_HUGETLB and VM_PFNMAP will be
handled by using the optimized path in the following separate patches for
bisectable sake.

Unmapping uprobe areas may need update mm flags (MMF_RECALC_UPROBES).
However it is fine to have false-positive MMF_RECALC_UPROBES according to
uprobes developer.

With the "detach vmas first" approach we don't have to re-acquire mmap_sem
again to clean up vmas to avoid race window which might get the address
space changed since downgrade_write() doesn't release the lock to lead
regression, which simply downgrades to read lock.

And, since the lock acquire/release cost is managed to the minimum and
almost as same as before, the optimization could be extended to any size
of mapping without incurring significant penalty to small mappings.

For the time being, just do this in munmap syscall path.  Other
vm_munmap() or do_munmap() call sites (i.e mmap, mremap, etc) remain
intact due to some implementation difficulties since they acquire write
mmap_sem from very beginning and hold it until the end, do_munmap() might
be called in the middle.  But, the optimized do_munmap would like to be
called without mmap_sem held so that we can do the optimization.  So, if
we want to do the similar optimization for mmap/mremap path, I'm afraid we
would have to redesign them.  mremap might be called on very large area
depending on the usecases, the optimization to it will be considered in
the future.

With the patches, exclusive mmap_sem hold time when munmap a 80GB address
space on a machine with 32 cores of E5-2680 @ 2.70GHz dropped to us level
from second.

munmap_test-15002 [008]   594.380138: funcgraph_entry: |
__vm_munmap() {
munmap_test-15002 [008]   594.380146: funcgraph_entry:      !2485684 us
|    unmap_region();
munmap_test-15002 [008]   596.865836: funcgraph_exit:       !2485692 us
|  }

Here the execution time of unmap_region() is used to evaluate the time of
holding read mmap_sem, then the remaining time is used with holding
exclusive lock.

[1] https://lwn.net/Articles/753269/

Link: http://lkml.kernel.org/r/1537376621-51150-2-git-send-email-yang.shi@linux.alibaba.com
Signed-off-by: Yang Shi &lt;yang.shi@linux.alibaba.com&gt;Suggested-by: Michal Hocko <mhocko@kernel.org>
Suggested-by: Kirill A. Shutemov <kirill@shutemov.name>
Suggested-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Matthew Wilcox <willy@infradead.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Add might_sleep() call to vfree() to catch potential sleep-in-atomic bugs
earlier.

[aryabinin@virtuozzo.com: drop might_sleep_if() from kvfree()]
  Link: http://lkml.kernel.org/r/7e19e4df-b1a6-29bd-9ae7-0266d50bef1d@virtuozzo.com
Link: http://lkml.kernel.org/r/20180914130512.10394-3-aryabinin@virtuozzo.com
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

vfree() might sleep if called not in interrupt context.  Explain that in
the comment.

Link: http://lkml.kernel.org/r/20180914130512.10394-2-aryabinin@virtuozzo.com
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

vfree() might sleep if called not in interrupt context.  So does kvfree()
too.  Fix misleading kvfree()'s comment about allowed context.

Link: http://lkml.kernel.org/r/20180914130512.10394-1-aryabinin@virtuozzo.com
Fixes: 04b8e946

 ("mm/util.c: improve kvfree() kerneldoc")
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

match_string() returns the index of an array for a matching string, which
can be used intead of open coded implementation.

Link: http://lkml.kernel.org/r/1536988365-50310-1-git-send-email-zhongjiang@huawei.com
Signed-off-by: zhong jiang <zhongjiang@huawei.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>